Technical Field
Embodiments described herein generally relate to processors. In particular, embodiments described herein generally relate to processors to add floating point numbers responsive to instructions.
Background Information
Floating point numbers are commonly used in processors, computer systems, and other electronic devices. One advantage of floating point numbers is that they allow a wide range of numerical values to be represented in a relatively compact numerical format and/or number of bits. The floating point numbers may have their bits apportioned into several constituent fields known as the sign, the significand, and the exponent of the floating point number. The sign, significand, base, and exponent may be related as follows:A=(−1)sign×significant×baseexponent 
The expression “(−1)sign” represents negative one raised to the power of the sign. This expression evaluates whether the floating point number is positive (+) or negative (−). For example, when the sign is integer zero the floating point number is positive, or alternatively when the sign is integer one the floating point number is negative. The significand includes a digit string of a length that largely determines the precision of the floating point number. The significand is also sometimes referred to as the significant digits, the coefficient, the fraction, or the mantissa. The radix point (e.g., the decimal point for decimal format or the binary point for binary format) is commonly implicitly assumed to reside at a fixed position (e.g., just to the right of the leftmost or most significant digit of the significand, which in some cases may be implicit). An example significand in binary may be “1.10010010000111111011011”. The digits of the significand to the right of the radix point (e.g., “10010010000111111011011”) may represent the fraction bits. The expression “baseexponent” represents the base raised to the power of the exponent. The base is commonly base 2 (for binary), base 10 (for decimal), or base 16 (for hexadecimal). The base is sometimes referred to as the radix. The exponent is also referred to as a characteristic or scale. Raising the base to the power of the exponent in effect shifts the radix point (e.g., from the implicit or assumed starting position) by the exponent number of digits. The radix point is shifted to the right if the exponent is positive, or to the left if the exponent is negative.
The Institute of Electrical and Electronics Engineers (IEEE) has standardized several different floating point formats in the standard IEEE 754. Representatively, a single precision floating point format has 32-bits and includes a 23-bit significand in bits [22:0], an 8-bit exponent in bits [30:23], and a 1-bit sign in bit [31]. A double precision floating point format has 64-bits and includes a 52-bit significand in bits [51:0], an 11-bit exponent in bits [62:52], and a 1-bit sign in bit [63]. Other floating point formats are also known in the arts, such as, for example, half precision floating point, extended double precision floating point, and quadruple precision floating point formats. Further details on floating point numbers and formats, if desired, are available in IEEE 754.